Many acoustic transducers or drivers use a moving coil dynamic driver to generate sound waves. In most transducer designs, a magnet energizes a magnetic flux within an air gap. The moving coil reacts with magnetic flux in the air gap to move the driver. Initially, an electromagnet was used to create a fixed magnetic flux in the air gap. These electromagnet based drivers suffered from high power consumption. More recently, acoustic drivers have been made with permanent magnets. While permanent magnets do not consume power, they have limited BH products, can be bulky and depending on the magnetic material, they can be expensive. In contrast, the electromagnet based drivers do not suffer from the same BH product limitations.
There is a need for a more efficient electromagnet based acoustic transducer that incorporates the advantages of electromagnets while reducing the effect of some of their disadvantages.